Conventionally, there have been proposed display devices with image capturing function capable of capturing an image of an object in the proximity of their displays by means of, for instance, photodetection elements such as photodiodes in the pixels. Such display devices with image capturing function are intended to be used as display devices for interactive communications and display devices with touch-screen function.
In a conventional display device with image capturing function, when well-known components such as signal lines, scan lines, thin film transistors (TFTs), and pixel electrodes are formed on an active matrix substrate using a semiconductor process, photodiodes are formed in the pixels at the same time. The conventional display devices with image capturing function are disclosed by JP 2006-3857 A and “A Touch Panel Function Integrated LCD Including LTPS A/D Converter”, T. Nakamura et al., SID 05 DIGEST, pp. 1054-1055, 2005, for instance.